R. Avigdor Nevenzal and R. Joshua Hoffman, based upon the teachings of both Nechama Leibovits, Zicronah Livracha, and R. Yeruchem of Mir, zt"l, shows us that Esau lacked a consistency between his heart and mouth: link 1, link 2

R. Shlomo Riskin explains that the essence of the dissagreement between Yitzchak and Rivkah was rooted in the unity of the birthright and the blessings of Avraham: link

Esau and the Birthright

R. Aharon Lichtenstein reminds us that one cannot approach Avodas HaShem with the attitude of “what's in it for me?” or with the view that it is a privilege, as opposed to a sacred responsibility: link 1, link 2